Effect of grape products on blood pressure: a systematic review and meta-analysis of randomized controlled trials

Previous studies have suggested that grape and its products may possess blood pressure (BP)-lowering properties. Due to inconsistencies in results, we aimed to systematically examine the effect of grape products on BP by conducting a meta-analysis of randomized controlled trials (RCTs). PubMed, Scopus, Web of Science (ISI), and Cochrane Library databases were comprehensively searched until March 2020. Human clinical trials which reported the effect of grape products supplementation on systolic BP (SBP) and diastolic BP (DBP) were included. Data were pooled using a random-effects model and expressed as a weighted mean difference (WMD) with a 95% confidence interval (CI). Twenty-eight studies comprising a total of 1344 subjects were included in our meta-analysis. The overall outcome of the meta-analysis indicates that grape products consumption can significantly reduce SBP (WMD: −3.40 mmHg, 95% CI: −6.55, −0.24, p = .03, I² = 93.4%) and DBP (WMD: −1.69 mmHg, 95% CI: −3.12, −0.27, p = .01, I² = 80.4%). This meta-analysis found a moderate and statistically significant reduction for either SBP or DBP with grape products compared with controls. Additional high-quality studies are needed to further evaluate the causal conclusions.